This invention relates to rotary mechanisms, and, more particularly, to elongated seals employed in such mechanisms which rub against the surface to be sealed in a direction substantially along their longitudinal extent, such as side seals in trochoidal engines or peripheral seals in slant axis rotary engines.
Prior art of possible relevance includes U.S. Pat. No. 3,834,845, issued to Siler on May 2, 1973.
Elongated seals in rotary mechanisms which rub against the surface to be sealed with a large longitudinal velocity component suffer frequent overheating. Typical of such seals are the end seals employed in trochoidal type mechanisms, oil seals employed in all rotary mechanisms and peripheral seals employed in slant axis rotary mechanisms.
The motion of such seals on the surface to be sealed is not unlike that of an ice skate with the result that a lubricating oil film cannot build up satisfactorily when the rubbing surfaces are extended in the direction of travel. Moreover, because such seals are forced to travel over a previously preheated surface, the heating of which has been caused by the forward portion of the same seal, oil viscosity is decreased thereby thinning the oil film and increasing friction for the trailing part of the seal.
A common consequence is a catastrophic failure due to scuffing of the engaging parts.
Heretofore, to avoid such scuffing, the prior art has resorted to a variety of measures, either singly or in combination. For example, in some cases, engines are derated by decreasing seal speeds to thereby drop the temperature at the rubbing surfaces. Unfortunately, under some conditions, such derating paradoxically decreases the oil film thickness so that the problem is not totally eliminated.
In some cases, an increased amount of oil is directed to the seals to cool the engaging parts and insure adequate lubrication. However, this approach increase oil consumption as well as emissions and is undesirable from these standpoints.
Most frequently, attempts to resolve the difficulty have centered about the use of expensive and exotic materials in the construction of the seals and the surfaces to be sealed.